1. Field of the Invention
The present invention relates to a recording medium Such as a magnetic recording disk incorporated into a hard disk drive (HDD), for example. In particular, the invention relates to a method of surface treatment for forming a lubricant film over the surface of the recording medium.
2. Description of the Prior Art
Organic acid such as oxalic acid and acetic acid exists over a diamond-like-carbon (DLC) surface layer of the magnetic disk as well as within a lubricant film formed to spread over the surface of the magnetic recording disk. The organic acid tends to get dissolved into water or moisture on the surface of the magnetic recording disk. The dissolved organic acid often induces corrosion or rust of the magnetic recording disk. The corrosion results in mounds on the surface of the magnetic recording disk.
For example, the lubricant film is subjected to exposure to ultraviolet rays in the process of production of the recording medium. Radiation of the ultraviolet rays serves to uniformly spread the lubricant film over the surface of the magnetic recording disk. In addition, the magnetic recording disk is allowed to obtain a higher repellency over the surface thereof. The magnetic recording disk may suffer from less friction. On the other hand, the radiation of the ultraviolet rays serves to generate organic acid of quite an amount over the surface of the magnetic recording disk, as well as in the lubricant film. Corrosion of the magnetic recording disk may be promoted.
A hard disk drive is supposed to require a smaller flying height of a flying head slider so as to realize the magnetic recordation of a still higher density. As the flying height gets smaller, the head slider suffers from a higher probability of colliding against corrosion mounds on the magnetic recording disk during rotation of the magnetic recording disk. The collision of the head slider against the corrosion mound may induce damages of the head slider and/or a read/write element on the head slider.
It is accordingly an object of the present invention to provide a method of surface treatment for a recording medium, which is capable of preventing generation of corrosion mounds on the recording medium.
According to a first aspect of the present invention, there is provided a method of surface treatment for a recording medium, comprising: radiating an ultraviolet ray over a lubricant film formed on the surface of the recording medium; and subjecting the recording medium to exposure to a base after radiation of the ultraviolet ray.
In general, when the ultraviolet ray is radiated over the lubricant film on the recording medium, the lubricant film is allowed to uniformly spread over the surface of the recording medium. At the same time, the repellency can be enhanced over the surface of the recording medium. The friction can be reduced on the recording medium.
Moreover, when the recording medium is exposed to the base, organic acid existing on the surface of the recording medium and/or in the lubricant film can be transformed into salt. The organic acid can thus be consumed. The organic acid can be washed off or removed from the surface of the recording medium and/or out of the lubricant film in this manner. Less organic acid greatly contributes to prevention of generation of corrosion mounds over a longer period. In particular, the ultraviolet radiation leads to generation of organic acid in quite a quantity on the surface of the recording medium and/or in the lubricant film. However, it has been proved that the base is remarkably effective to reduce the quantity of the corrosion mounds on the recording medium.
The base may be a weak base. In particular, the base may be an amine compound. Such an amine compound may include an aliphatic amine compound, for example.
When the recording medium is exposed to the base, the recording medium may be dipped into a solution including the base. The solution may comprise a solvent such as hydrofluoroether compound, for example. The base may be resolved into the solvent.
The lubricant film may comprise a perfluoroether compound, for example. In particular, the perfluoroether compound may be a perfluoropolyether compound having piperonyl radicals at both terminals.
The ultraviolet ray preferably has a wavelength equal to or smaller than 200 nm. The ultraviolet ray of this wavelength is supposed to realize an efficient generation of ozone molecules out of oxygen molecules. Accordingly, reaction of oxidation can be promoted over the surface of the recording medium. The oxidation serves to uniformly spread the lubricant film over the surface of the recording medium.
According to a second aspect of the present invention, there is provided a method of surface treatment for a recording medium, comprising: forming a lubricant film over the surface of the recording medium; and subjecting the recording medium to exposure to a base.
When the recording medium is exposed to the base, organic acid existing on the surface of the recording medium and/or in the lubricant film can be transformed into salt. The organic acid can thus be consumed. The organic acid can be washed off or removed from the surface of the recording medium and/or out of the lubricant film in this manner. Less organic acid greatly contributes to prevention of generation of corrosion mounds over a longer period.